Review of results of HF scattering by artificial ionospheric turbulence obtained with UTR-2 radio telescope

The effects of modification of a high-latitude ionosphere by high-power HF radio waves. Part 1. Results of multi-instrument ground-based observations

“…plasma into strongly stretched magnetic-field aligned electron-density irregularities were detected even in the first experiments on the ionosphere modification by a highpower HF wave [9]. The excitation of small-scale irregularities in all the earlier experiments based on HF heating facilities such as Sura, Arecibo, EISCAT/Heating, HAARP, and SPEAR located at the mid and high latitides (see, e.g., [10][11][12][13][14][15][16][17][18][19]), was observed in the upper-hybrid resonance region during reflection of an O-mode highpower HF from the ionosphere or at heating frequencies slightly above the critical frequency f oF 2 when the Omode wave is approximately equal to the upper-hybrid frequency at the F 2 -layer maximum, i.e., f H = (f 2 oF 2 + f 2 ce ) 1/2 , where f ce is the electron gyrofrequency. As was mentioned, the excitation of small-scale artificial ionospheric irregularities due to the thermal (resonant) instability during the ionosphere heating by a an X-mode high-power HF radio wave is not possible since the Xmode is always reflected from the region located below the resonant one.…”

The “Sura” facility: Study of the atmosphere and space (a review)

“…Measurements of the Doppler spectra of aspect-scattered signals in the "Sura" experiments yielded the following results: i) the spectrum consists of a narrow-banded (of width about 0.2 Hz) central part and a broadband (of width about 1 Hz) part, which relaxes notably faster after the PW is switched off; ii) quasiperiodic variations in the scattered-signal parameters with a period of about 2-5 min are detected; iii) stable splitting of the scattered-signal spectra (∆f ∼ 0.2-0.8 Hz) is observed (the effect can be interpreted as the relative motion of inhomogeneities with a velocity of about 3 m/s); iv) it is found that the signal intensity and the spectrum width are minimum for f 0 ≈ nf ce and turn out to be larger for f 0 > nf ce than for f 0 < nf ce [24,40,66,67]. …”

“…Meter and decameter inhomogeneities also ensure aspect scattering of short and ultrashort radio waves. A detailed description of AIT and its theoretical consideration are presented in surveys [3,6,10,24,25,[32][33][34][35][36][37][38][39][40] and special journal issues [41][42][43][44][45][46][47][48]. In what follows we give a short characteristic of the studied phenomena, focusing primarily on recent achievements obtained with the use of "Sura.…”

“…Spectral and dynamic properties of the SFAI are described in detail in [25,35,37,39,40]. Here we only mention that the threshold field of the SFAI generation amounts to E thr ∼ 40 mV/m, which is lower than both the theoretical values for the TPI and the threshold of the SPI.…”

The polar-ionosphere phenomena induced by high-power radio waves from the spear heating facility

“…Stimulated electromagnetic emission was observed for the first time by using the EISCAT/Heating facility [5]. Intense experimental studies of AFAIs (see, e.g., [6][7][8][9][10][11][12][13][14][15]) and stimulated electromagnetic emission (see, e.g., [16] and references therein and [17][18][19]) using HF heaters such as the facility in Arecibo, the "Sura," EISCAT/Heating, and HAARP facilities located at mid-and high latitudes have been performed in the last three decades.…”